Is only playing a single role the best way to climb?

I'm trying to learn the best way to climb here,

I've been playing LoL since season 2 and have slowly climbed my way up the ladder every year but this year I started in gold and stayed in gold, and I really cannot figure out why. I'm thinking I might be trying to be TOO good at the game? I can play every champion fairly decently. (Like I know their basic mechanics, play-styles, itemization and so on) but I was only able to get to gold 1 and then back slid all the way down to Gold 4 with a very bad end of season push for Plat.

Since I understand the fundamentals of the game, setting up slow pushes, champion match ups, itemization, vision and timing for neutral objections and rotations. I'm wondering if it's better to just focus down on one lane only instead of trying to be the jack of all trades? I linked to my champion performance because maybe someone can see between the lines better than I can

I'm open to criticism, if you think you see something, feel free to mention it!